Stabilized cellulosic material



United States Patent OfiFice 3,234,234 Patented Nov. 8, 1966 3,234,234lTABliLlZED CELLULQJSIIC MATERHAL Laurence R. ll. Hervey, West Concord,and Richard P.

Tschirch, Westwood, Mass, assignors, by mesne assignments, to (tlinMatlnieson Chemical Corporation, New

York, N.Y., a corporation of Virginia No Drawing. Filled Sept. 3, 1963,5oz. No. 306,287

8 Claims. (Cl. 117l54) The present invention relates to thestabilization of celluloslc materials. More particularly, the presentinvention resides in a process for the stabilization of cellulosicmaterials utilizing certain hydrazine-containing compounds and t thestabilized cellulosic materials thereby obtained.

Cellulosic materials are widely used in industiy and commerce, due in alarge part to their low cost and wide availability. Certaindisadvantagesv are, however, attendant upon their use for certainapplications, namely, thermal stability and stabilityupon exposure tocorrosive materials.

An illustrative application where this type of property is essential isin transformer boards. A transformer board is a paper board used as aninsulation barrier in oil immersion transformers. This board is subjectboth to thermal degradation and attack by acids formed in the oils asthey age. Thus, it is highly desirable that the. cellulosic board becapable of considerable resistance to this type of corrosion. Inaddition, it is highly desirable to provide paper products and cottonfiber products and various other cellulosic products which are resistantto elevated temperatures for extended periods of time. The advantages ofsuch a stabilized product are readily apparent when the wide andconsiderable use of these products is realized. 0

Increasing the thermal stability of paper is of particular importance inelectrical applications, for example, in paper tapes which should retaintheir strength and pliability during long exposure to elevatedtemperatures. Another application for a thermally stable paper productis in publication paper printing with heat set inks. In printing withheat set inks the paper becomes very hot and thus embrittled. Thisembrittlement causes difficulties when the printed paper web issubsequently folded in the fabrication of books and magazines. Inaddition, it is, of course, highly desirable to improve the long termstability of paper at room temperatures in an application, for example,such as the preservation of documents. A further application forstabilized cellulosic products is in the stabilization of such productsas rayon tire cord which by necessity is subjected to rigorous useconditions. The foregoing are merely typical applications where thistype of stability is necessary.

Numerous materials have been suggested as stabilizers for cellulosicmaterials to overcome the foregoing disadvantages. However, generallythese materials have one or more disadvantages, for example, the levelof stability may be low, there may be accompanying degradation of otherproperties, for example, color degradation which is especially importantin certain areas, and the cost of the stabilizer may be prohibitivelyhigh.

Accordingly, it is an object of the present invention to provide aprocess for the stabilization of cellulosic products in general, and astabilized cellulosic material.

It is a further and particular object of the present invention toprovide a simple, convenient, expeditious and inexpensive process andstabilized product as aforesaid.

It is a further object of the present invention to provide a processwith particular reference tothe foregoing problems in the use ofcellulosic materials, namely, a process that achieves a cellulosicmaterial having improved thermal and corrosion stability.

it is a further object of the present invention to provide a processwhich is characterized by little or no degradation of the physical orchemical characteristics of the cellulose, for example, color stability.

Further objects and advantages of the present invention will appearhereinafter.

In accordance with the present invention is has now been found that theforegoing objects and advantages may be readily accomplished and aprocess obtained for the stabilization of cellulosic materials. Inaddition, the present invention obtains a stabilized cellulosic materialhaving surprisingly improved properties.

The process of the present invention comprises contasting the cellulosicmaterial to be stabilized with at least 0.1 and preferably from 0.5 to15 percent by weight of cellulosic material and optimally from 1 to 9percent of a hydrazide selected from the group consisting of thefollowing compounds and mixtures thereof:'

1 RCONHNH2 n RCONHNHCOR n1 nrconnnnp wherein each R is independentlyselected from the group consisting of hydrogen and alkyl containing from1 to 8 carbon atoms and wherein R is selected from the group consistingof (-CH wherein n is an integer having a value of 0-5, and an alkyleneof 2-6 carbon atoms interrupted by from 1 to 2 atoms selected from thegroup consisting of oxygen and sulfur. The stabilized cellulosicmaterial of the present invention comprises a cellulosic material havingsaid hydrazide in an amount of at least 0.1 percent by weight ofcellulosic material incorporated therein.

As aforesaid the process of the present invention comprises simplycontacting the cellulosic material with the requisite quantity of thestabilizer of the present invention. Naturally the choice of specificmethod of contact will vary widely depending upon the application andthe particular cellulosic material employed, e.g., in the stabilizationof transformer boards, it is possible to simply add the stabilizer orstabilizers to the oil or incorporate them in the board itself in somestage of its formation. In the stabilization of paper sheets orcellulosic textiles, the sheets or textiles may be impregnated to thedesired dry pickup with aqueous solutions of the desired chemical, runthrough rubber rolls and air dried. Alternatively, the stabilizer may beincorporated in the cellulosic paper or textile in some preliminarystage of its formation. The foregoing is simply intended to beillustrative of the fact that the specific manner of contacting is notespecially critical. It is required only that the chosen cellulosicmaterial be contacted with or impregnated with or immersed in therequisite concentration of stabilizer of the present invention, forexample, by dipping in either a solution or suspension of the desiredstabilizer or spraying, etc.

In accordance with the present invention the cellulosic material iscontacted with at least 0.1 percent by weight of the cellulosic materialof one or more stabilizers of the present invention. Naturally, theparticular quantity of stabilizer employed will vary depending upon theparticular application desired, the particular cellulosic material andthe particular stabilizer. The upper amount is not especially critical,being limited only by economic factors, the particular applicationdesired, and the particular stabilizer. In general, however, from 0.5 to15 percent is employed, and optimally from 1 to 9 percent by weight ofthe cellulosic material.

3 4 The particular stabilizer of the present invention may Table I beany monoor di-hydrazide or mixtures thereof hav- Tensile Strengthretained, mg the aforesaid structural formulas, namely, Hydrazidezpercent of Original RCONHNH None 54 RCONHNHCOR 5 Acetic hydraZi-de 82R'(CONHNH2)2 Adipic dihydrazide 80 wherein each R is independentlyselected from the group Dicy'andiamide 1 consisting of hydrogen andalkyl containing from 1 to 8 Example 2 carbon atoms and wherein R isselected from the group consisting of wherein n is an integer having 10The procedure of Example 1 was repeated and the a value of and alkyleneof carbon atoms tensile strengths were measured on strips cut 1n themaintemlpted by from 1 to 2 atoms Selected from the chine direction ofthe board with the following results: group consisting of oxygen andsulfur. Exemplificative T bl 2 dihydrazides which may be readilyemployed include, but are not limited to, the following: oxalicdihydrazide, H d Tenslle malonic dihydrazide, succinic dihydrazide,glutanic diy percent 0 Ongma 34 hydrazide, adipic dihydrazide, pimelicdihydrazide, digi 1 -1 39 glycolic dihydraz-ide, thiodiglycolicdihy-drazide, etc. Ex-

3. i e 50 amples of representative hydrazides of monobasic acids 20 Ce ytall 6 include, but are not limited to, acetic hydraz-ide, diformicExample 3 hy-drazide, 'di-acetic hydrazide, propionic hydrazide, etc.Unsized fa a er beet were jm re mated with a Especially i q q Stabilize?in .aqcordance W l ous solu-tions -o i s aric ms h ydrazides anfi driedto ad d 5 present lllnvenmon i pi activity and aviillablhiy percent drypickup of hydrazide. The sheets Were aged l acetic hydrazlde dlhydrazrdeand dl'glycohc in an air-circulating oven at 300 F. for 24 hours, conlditioned at 68 F. and 50 percent relative humidity for It IS asurprising feature of the present invention that 24 hours and the foldendurance was measured with the the stabilizers presently employed sosignificantly imfollowing results. prove the stability of cellulosicmaterials in the entire Table 3 range of compounds covered herein. It isespecially surprising that the stabilizers of the present invention areFold endurance Ef generally superior to conventional stabilizersemployed for Hydralldei P 0f Oflglnal this purpose, such as, forexample, dicyandiamide. It is PQ further especially surprising that thestabilizers of the Adlplc dlhydrallde 33 subject invention are markedlysuperior to, for example, 35 The data of this accelerated test show asignificant imdicyandiamide, with respect to color stability. provementin fold endurance by the incorporation of the The stabilizer of thepresent invention may be conhydrazides and are an indication of theimprovement obveniently utilized, as indicated above, in an aqueoussolutained in long term aging of paper at normal temperation or in anyother medium suitable to the particular tures. application desired. Inaddition the aqueous or other solu- Example 4 i niwdlfied. for gamculara for Strips of 1 x 8 inch unbleached cotton cloth were satui gg f i ggy z z gi Zi g g ty: "221 rated with 3.4 percent aqueous solutions of thehydrazides, h d y p a a ula a p H ati n squeezed through rubber rollsand an dried. tDry pickup fi epen 'aggm lfi e p 16 pp 6 o was 5 percent.The strips were heated in an air-circuc 2t 72 were conditioned at 68 F.and percent relative hu- EXAMPLE 1 midity for 24 hours and then thetensile strengths were A stabilizer mixture for oil immersiontransformer Hwasufed, with the following results! board was prepared bymixing thorough-1y 60 parts by Table 4 weight of a hydrazide (see tablebelow), 35 parts of 50 melamine and 5 parts of an acrylicacid-acrylarn-ide co- Tensile Strength Retained, polymer. Percent ofOriginal Into 160 grams of a commercial transformer oil was Hydrazideintroduced 0.34 gram of the above stabilizer mixture and 24Hours 72Hours the whole was heated to 175 C.

Test strips were cut in the cross machine direction None 63 45 from 100percent rag stock board 15 mils thick. The gg gggg g gigg 3g 23 /2 x 4inch strips were immersed in the heated oil for Adiplc Dih drazideIIIII:68 e1 70 hours. The strips were removed, excess oil wiped ofi,conditioned by storing for 24 hours at 68 F. and 50 per- E l 5 centrelative humidity. xamp e The average tensile strength of the teststrips was de- The procedure of Example 3 was repeated with thetermine-d as follows: following results:

Talble 5 Fold Endurance Retained, Percent of Tensile Original StrengthRe- Hydrazide tained Percent of Original 24 Hours 48Hours 72 Hours After72 Hours None 5 1 0.3 Diglycollc Dihydrazlde 32 13 9 81 Acetic Hydrazide16 6 1 78 Acetic Hydrazide 60 Melamine 35% 20 5 2 78 Polyacrylamide 5EXAMPLE 6 lowing stabilizers added showed good color retention, al-,

though not as good as the control,

adipic dihydrazide, diacetic hydrazide, diformic hydrazide;

paper sheet treated with dicyandiamide had a generally darker color andwas spotty.

Similar results were obtained with the unbleached cotton cloth treatedin accordance with Example 4 (after 72 hours aging), i.e., samplestreated with dicyand-iamide showed severe color degradation; whereas,hydrazide treated samples showed good color retention.

This invention may be embodied in other forms or carried out in otherways without departing from the spirit or essential characteristicsthereof. The present embodiment is therefore to be considered as in allrespects illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims, and all changes which comewithin the meaning and range of equivalency are intended to be embracedtherein.

What is claimed is:

1. A stabilized cellulosic material which comprises a cellulosicmaterial impregnated with at least 0.1 percent by weight of thecellulosic material of a hydrazide selected from the group consisting ofthe following compounds and mixtures thereof:

1 Rcornama n RCONHNHCOR (III) R(CONHNHZ)2 wherein each R isindependently selected from the group consisting of hydrogen and alkylcontaining from 1 to 8 carbon atoms and wherein R is selected from thegroup consisting of (CH wherein n is an integer having a value of 0 to 5and an alkylene of 2 to 6 carbon atoms interrupted by from 1 to 2 atomsselected from the group consisting of oxygen and sulfur.

2. A stabilized cellulosic material according to claim 1 wherein from0.5 to 15 percent by weight of said hydrazide is employed.

3. A stabilized cellulosic material according to claim 1, wherein saidhydrazide is acetic hydrazide.

4. A stabilized cellulosic material according to claim 1, wherein saidhydrazide is adipic dihydrazide.

5. A stabilized cellulosic material according to claim 1, wherein saidhydrazide is diglycolic dihydrazide.

6. A stabilized cellulosic material according to claim 1 wherein saidcellulosic material is transformer board and wherein said hydrazide ispresent in an amount from 0.5 to 15% by weight.

7. A stabilized cellulosic material according to claim 1, wherein saidcellulosic material is paper and wherein said hydrazide is present in anamount from 0.5 to 15% by weight.

8. A stabilized cellulosic material according to claim 1, wherein saidcellulosic material is textile and wherein said hydrazide is present inan amount from 0.5 to 15 by weight.

References Cited by the Examiner UNITED STATES PATENTS 2,050,196 8/1936Sebrell l17136 2,161,808 6/1939 Finlayson et al. 117139.4 2,665,2301/1954 Buckwalter l17-l44 2,904,387 9/1959 Holbrook et al. 1l7-139.4 X2,904,389 9/1959 Thomas et al. 117139.4 X 2,904,390 9/1959 Doerr et al.117-139 X 3,230,107 1/1966 Sadler 1l7l54 X WILLIAM D. MARTIN, PrimaryExaminer.

T. G. DAVIS, Assistant Examiner.

1. A STABILIZED CELLULOSIC MATERIAL WHICH COMPRISES A CELLULOSE MATERIALIMPREGNATED WITH AT LEAST 0.1 PERCENT BY WEIGHT OF THE CELLULOSICMATERIAL OF A HYDRAZIDE SELECTED FROM THE GROUP CONSISTING OF THEFOLLOWING COMPOUNDS AND MIXTURES THEREOF: